2008 328i sedan w/ Hifi(I believe) and the Sony "Tune Tray" Bluetooth head unit, which I'm very happy with.
Subs and Amps are now next up and within reach; first thought possibly replace the underseat subs with the SWS, add a larger sub-bass stealth in the trunk, either side pocket, and applicable Amps for both.
This is a pricey job I know, and may be done in chunks, looking for ideas.
Thanks!